About six months later, the seventh conference took place, which added the traitorous human Mavic Chen, the supposed Guardian of the Solar System, to the Alliance in order to obtain the taranium core needed to complete the Time Destructor they would use to take over the galaxy. Zephon and Celation took the places of Sentreal and Warrien. Chen acted as the informal leader, along with the Black Dalek. The Daleks requested a time machine to be sent from Skaro to pursue the First Doctor and retrieve the taranium core after its theft, the Doctor and others having overpowered Zephon and the Doctor disguising himself as him.

Afterwards, the Daleks held Zephon accountable and executed him. When the fake core was retrieved and placed in the Time Destructor, Chen and Malpha were complicit in the Daleks' plan to test it on Trantis, being wary of his power as leader of the largest of the Outer Galaxies. Though the Destructor failed, the Daleks then executed him anyway. At the final conference involving the six surviving delegates of the Galactic Council, Mavic Chen tried to take over the Council. The delegates attacked Chen, but Chen shot and killed Gearon. The alliance then ended when Mavic Chen and the Daleks turned against each other.

The Dalek Supreme left the delegates fighting amongst themselves and ordered them to be imprisoned in the headquarters, planning to destroy the headquarters with them inside. As the others attacked Chen, he shot and killed Gearon before they realised they had been betrayed. However, Sara Kingdom and Steven Taylor freed Chen, Malpha, Beaus and Celation, and they agreed to form a new alliance to stop the Daleks. Three of the delegates escaped but Chen stayed behind to try to renegotiate with the Daleks, faking his death by destroying his ship and taking Sara and Steven prisoner. Losing patience, the Daleks quickly exterminated him. The Doctor then stole the Time Destructor and by operating it destroyed the Daleks by reversing time on the planet. (TV: The Daleks' Master Plan) This event started the Great War (PROSE: The Evil of the Daleks)